1. Field of the Invention
This invention relates to telecommunication networks. More particularly, the invention concerns the control of voice calls in an IP network.
2. Description of the Prior Art
By way of background, IP (Internet Protocol) packet networks are now being used to provide bearer pathways for voice communications. In these systems, voice calls between communicating IP endpoints, such as IP telephones, are placed on through-connections established by network switching nodes. Such connections are router-based and are generally under the control of the endpoints themselves.
What is lacking in conventional VoIP (Voice over IP) systems is an interface for implementing bearer path connection control and manipulation at packet network points of entry. In particular, there is no mechanism for positive enforcement of bearer connection establishment and teardown. Connections cannot be terminated except by one or both of the IP endpoints. This means that parties using IP telephones might continue to talk even though billing for a call has stopped (i.e., because bearer path remains open). Conversely, billing might continue after the parties have ended the call.
Conventional VoIP systems also lack ability to provide pivot points for VoIP lines and trunks carrying the IP bearer traffic into and out of an IP core network. Such pivot points are currently only provided by LAGs (Line Access Gateways) and TAGs (Trunk Access Gateways) that carry purely TDM bearer traffic or which interwork between TDM bearer traffic and packet orientated (e.g., ATM, IP) bearer traffic. Without pivot points on the trunk side of an IP network entry point, packet switches need to be aware of when another switch in a call manipulates the bearer path. The bearer path thereby becomes a shared resource that all switches will jointly use to provide their own services. This greatly increases the complexity of implementing services because feature interactions cross switch boundaries. Without pivot points on the line side of an IP network entry point, packet switches cannot perform call redirection and insert/remove service circuits in established connections to provide the usual services available to TDM (Time Division Multiplexing) lines. Such services include N-way bridging, announcement playback, tone generation, tone detection, speech recognition, and multicasting.
In addition to the forgoing disadvantages of conventional VoIP systems, certain law enforcement statutes, such as the Communications Assistance for Law Enforcement Act (CALEA) (47 U.S.C. 1001 et seq.), require that a call involving a surveillance subject remain under surveillance even after the subject is no longer a participated in the call. Because count orders for CALEA surveillance may limit the geographic scope over which the surveillance may be performed, there is a need to ensure that the bearer path for a call stays within the geographic bounds within which it may be surveilled. If IP endpoints are able to establish a bearer path using conventional routing, there is no such guarantee.
Accordingly, there is a need in a packet network providing voice connection service for an interface system that implements bearer path connection control and manipulation at packet network points of entry. The same capability is also needed when data and voice calls are transported over IP.